Heat efficient portable fuel cell systems

ABSTRACT

The invention relates to fuel cell systems with improved thermal efficiency. The systems include a fuel cell that generates electrical energy using hydrogen and a fuel processor that produces hydrogen from a fuel. Some heat efficient systems described herein include a thermal catalyst that generates heat when the catalyst interacts with a heating medium. The heat is used to heat the fuel cell. The thermal catalyst may be disposed in proximity to the fuel cell, or remote from the fuel cell and a heat transfer pipe conducts heat from the catalyst to the fuel cell. Another thermally efficient embodiment uses a recuperator to transfer heat generated in the fuel cell system to incoming fuel. A fuel cell package may also include a multi-layer insulation arrangement to decrease heat loss from the fuel cell and fuel processor, which both typically operate at elevated temperatures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/314,810, currenrly U.S. Pat. No. 7,666,539 filed Dec. 20, 2005 andentitled “Heat Efficient Portable Fuel Cell Systems”, which a) claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Patent ApplicationNo. 60/638,421 filed on Dec. 21, 2004; and b) is a continuation-in-partof and claims priority under 35 U.S.C. §120 to U.S. patent applicationSer. No. 10/877,771 currently U.S. Pat. No. 7,763,368 filed Jun. 25,2004, which claims priority under 35 U.S.C. §119(e) from i) U.S.Provisional Patent Application No. 60/482,996 filed on Jun. 27, 2003,ii) U.S. Provisional Patent Application No. 60/483,416 and filed on Jun.27, 2003, and iii) U.S. Provisional Patent Application No. 60/482,981and filed on Jun. 27, 2003; each of the above mentioned patentapplications is incorporated by reference in its entirety herein for allpurposes.

BACKGROUND OF THE INVENTION

The present invention relates to fuel cell technology. In particular,the invention relates to systems and methods for improving the thermalefficiency of a fuel cell system.

A fuel cell electrochemically combines hydrogen and oxygen to produceelectricity. The ambient air readily supplies oxygen; hydrogenprovision, however, calls for a working supply. The hydrogen supply mayinclude a direct hydrogen supply or a ‘reformed’ hydrogen supply. Adirect hydrogen supply employs a pure source, such as compressedhydrogen in a pressurized container, or a solid-hydrogen storage system,such as a metal-based hydrogen storage device.

A reformed hydrogen supply processes a fuel (or fuel source) to producehydrogen. The fuel acts as a hydrogen carrier, is manipulated toseparate hydrogen, and may include a hydrocarbon fuel, hydrogen bearingfuel stream, or any other hydrogen fuel such as ammonia. Currentlyavailable hydrocarbon fuels include methanol, ethanol, gasoline, propaneand natural gas. Liquid fuels offer high energy densities and theability to be readily stored and transported.

Consumer electronics devices and other portable electrical powerapplications currently rely on lithium ion and other batterytechnologies. Portable fuel cell systems that generate electrical energyfor portable applications such as electronics devices would be desirablebut are not yet commercially available.

Thermal inefficiencies in a portable fuel cell system waste energy andundesirably require more fuel to be consumed and carried. Techniquesthat increase efficiency of a portable fuel cell system would bebeneficial.

SUMMARY OF THE INVENTION

The present invention relates to fuel cell systems with improved thermalefficiency. The systems include a fuel cell that generates electricalenergy using hydrogen and a fuel processor that produces hydrogen from afuel. The fuel processor includes a reformer and a burner that heats thereformer.

In one embodiment, heat efficient systems described herein include athermal catalyst, disposed outside the fuel cell, operable to produceheat when a heating medium interacts with the thermal catalyst. The heatis used to heat the fuel cell when the fuel cell is below a thresholdtemperature such as its minimum operating temperature. For example, thethermal catalyst may comprise a catalyst that generates heat in thepresence of methanol, such as unused methanol in the burner exhaust. Thethermal catalyst may be disposed in proximity to the fuel cell, such asin contact with one or more heat transfer appendages that permitexternal thermal management of internal portions of fuel cell stack. Inanother embodiment, the catalyst is remote from the fuel cell and a heattransfer pipe conducts heat from the catalyst to the fuel cell.

Another thermally efficient embodiment uses a recuperator to transferheat generated in the fuel cell system to incoming fuel.

A fuel cell package may also include a multi-layer insulationarrangement to decrease heat loss from the fuel cell and fuel processor,which both typically operate at elevated temperatures. The insulationalso increases thermal efficiency of the fuel cell system by keepingmore heat internal to the package.

In one aspect, the present invention relates to a fuel cell system forproducing electrical energy. The fuel cell system comprises a fuelprocessor that includes a) a reformer configured to receive reformerfuel and including a catalyst that facilitates the production ofhydrogen from the reformer fuel, and b) a burner configured tocatalytically process burner fuel to generate heat. The fuel cell systemalso comprises a fuel cell including a fuel cell stack that isconfigured to produce electrical energy using hydrogen output by thefuel processor, and including a heat transfer appendage that includes aportion arranged external to the fuel cell stack and is in conductivethermal communication with an internal portion of the fuel cell stack.The fuel cell system further includes a thermal catalyst disposedoutside the fuel cell that produces heat when a heating medium interactswith the thermal catalyst. The fuel cell system additionally includesplumbing configured to transport the heating medium from the burner tothe thermal catalyst.

In another aspect, the present invention relates to a fuel cell systemthat includes a fuel processor, fuel cell, a catalyst containmentsystem, and fluidic plumbing. The catalyst containment system includes aset of walls that are configured to hold a thermal catalyst outside thefuel cell and permit a heating medium to pass into the catalystcontainment system. The thermal catalyst and heating medium are selectedto produce heat when the heating medium interacts with the thermalcatalyst. The plumbing is configured to transport the heating medium tothe catalyst containment system, wherein an outlet of the plumbing isless than about 2 centimeters from thermal catalyst nearest to theoutlet.

In yet another aspect, the present invention relates to a fuel cellsystem that includes a fuel processor, fuel cell, thermal catalyst, heattransfer pipe and fluidic plumbing. The thermal catalyst is disposedoutside the fuel cell and produces heat when a heating medium interactswith the thermal catalyst. The heat transfer pipe is configured toconductively transfer heat from the thermal catalyst to the fuel cellstack. The plumbing is configured to transport the heating medium fromthe burner to the thermal catalyst.

In still another aspect, the present invention relates to a method forproviding a fuel to a fuel cell system including a fuel cell and a fuelprocessor. The method includes providing fuel to a burner in the fuelprocessor; and combusting the fuel in the burner to generate heat. Themethod also includes transferring at least a portion of the heat fromthe burner to a reformer included in the fuel processor. The methodfurther includes increasing an amount of the fuel provided to the burnersuch that more fuel is provided to the burner than is used in the burnerto generate heat. Exhaust is then provided from the burner to a thermalcatalyst that produces heat when the burner exhaust interacts with thethermal catalyst. The method then includes transferring the heat fromthe thermal catalyst to the fuel cell.

In another aspect, the present invention relates to a fuel cell systemthat includes a fuel processor, fuel cell, and fuel pre-heating usingheat generated in the system. The fuel cell system also includesplumbing configured to transport a reformer fuel to the reformer; andplumbing configured to transport a burner fuel to the burner. The fuelcell system further includes a recuperator that is configured totransfer heat generated in the fuel cell system to the reformer fuel orthe burner fuel.

These and other features of the present invention will be described inthe following description of the invention and associated figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a fuel cell package including a fuel processor inaccordance with one embodiment of the present invention.

FIG. 1B illustrates schematic operation for the fuel cell package ofFIG. 1A in accordance with a specific embodiment of the presentinvention.

FIG. 2A illustrates a top perspective view of components included in anexemplary fuel processor in accordance with a specific embodiment of thepresent invention.

FIG. 2B illustrates a cross-sectional front view of a central portion offuel processor of FIG. 2A.

FIG. 3A illustrates a simplified cross sectional view of a fuel cellstack in accordance with one embodiment of the present invention.

FIG. 3B illustrates an outer top perspective view of a fuel cell stackand fuel cell in accordance with another embodiment of the presentinvention.

FIG. 3C illustrates a top perspective view of a stack of bi-polar platesin accordance with one embodiment of the present invention.

FIG. 4 shows another embodiment of the invention where catalyst disposedin proximity to the fuel cell is configured to interact with exhaustfrom a reformer.

FIGS. 5A-5C show three exemplary catalyst containment systems thatachieve catalyst containment in accordance with several embodiments ofthe present invention.

FIG. 6 shows a simplified illustration of a proximal heating system inaccordance with one embodiment of the present invention

FIG. 7 shows a method for providing fuel in a fuel cell system inaccordance with one embodiment of the present invention.

FIG. 8 shows a fuel cell system in accordance with another embodiment ofthe present invention.

FIG. 9 shows a fuel cell system that includes a recuperator inaccordance with one embodiment of the present invention.

FIGS. 10A-10C show three exemplary recuperators that heat an incomingfuel in accordance with the present invention.

FIG. 11 shows a simplified cross section of a fuel cell system inaccordance with a specific embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described in detail with reference to a fewpreferred embodiments as illustrated in the accompanying drawings. Inthe following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art, that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process steps and/or structureshave not been described in detail in order to not unnecessarily obscurethe present invention.

Fuel Cell Systems

Fuel cell systems that benefit from the present invention will first bedescribed. FIG. 1A illustrates an exemplary fuel cell system 10 forproducing electrical energy in accordance with one embodiment of thepresent invention. The ‘reformed’ hydrogen system 10 processes a fuel 17to produce hydrogen for supply to fuel cell 20. As shown, the reformedhydrogen supply includes a fuel processor 15 and a fuel storage device16.

Storage device 16 (or ‘cartridge’) stores a fuel 17, and may comprise arefillable and/or disposable fuel cartridge. Either design permitsrecharging capability for a fuel cell system or electronics device byswapping a depleted cartridge for one with fuel. A connector on thecartridge 16 interfaces with a mating connector on an electronics deviceor portable fuel cell system to permit fuel to be withdrawn from thecartridge. In one embodiment, the cartridge includes a bladder thatcontains the fuel and conforms to the volume of fuel in the bladder. Anouter rigid housing provides mechanical protection for the bladder. Thebladder and housing permit a wide range of portable and non-portablecartridge sizes with fuel capacities ranging from a few milliliters toseveral liters. In one embodiment, the cartridge is vented and includesa small hole, single direction flow valve, hydrophobic filter, or otheraperture to allow air to enter the fuel cartridge as fuel 17 is consumedand displaced from the cartridge. This type of cartridge allows for“orientation” independent operation since pressure in the bladderremains relatively constant as fuel is displaced. A pump may draw fuel17 from the fuel storage device 16. Cartridges may also be pressurizedwith a pressure source such as foam or a propellant internal to thehousing that pushes on the bladder (e.g, propane or compressed nitrogengas). Other fuel cartridge designs suitable for use herein may include awick that moves a liquid fuel from locations within a fuel cartridge toa cartridge exit. In another embodiment, the cartridge includes‘smarts’, or a digital memory used to store information related to usageof the fuel cartridge.

A pressure source (FIG. 1B) moves the fuel 17 from cartridge 16 to fuelprocessor 15. Exemplary pressure sources include pumps, pressurizedsources internal to the cartridge (such as a compressible foam orspring) that employ a control valve to regulate flow, etc. In oneembodiment, a diaphragm pump controls fuel 17 flow from storage device16. If system 10 is load following, then a control system meters fuel 17flow to deliver fuel to processor 15 at a flow rate determined by arequired power level output of fuel cell 20 and regulates a controlleditem accordingly.

Fuel 17 acts as a carrier for hydrogen and can be processed ormanipulated to separate hydrogen. As the terms are used herein, ‘fuel’,‘fuel source’ and ‘hydrogen fuel source’ are interchangeable and allrefer to any fluid (liquid or gas) that can be manipulated to separatehydrogen. Fuel 17 may include any hydrogen bearing fuel stream,hydrocarbon fuel or other source of hydrogen such as ammonia. Currentlyavailable hydrocarbon fuels 17 suitable for use with the presentinvention include gasoline, C₁ to C₄ hydrocarbons, their oxygenatedanalogues and/or their combinations, for example. Other fuel sources maybe used with a fuel cell package of the present invention, such assodium borohydride. Several hydrocarbon and ammonia products may also beused. Liquid fuels 17 offer high energy densities and the ability to bereadily stored and shipped.

Fuel 17 may be stored as a fuel mixture. When the fuel processor 15comprises a steam reformer, for example, storage device 16 includes afuel mixture of a hydrocarbon fuel and water. Hydrocarbon fuel/watermixtures are frequently represented as a percentage of fuel in water. Inone embodiment, fuel 17 comprises methanol or ethanol concentrations inwater in the range of 1-99.9%. Other liquid fuels such as butane,propane, gasoline, military grade “JP8”, etc. may also be contained instorage device 16 with concentrations in water from 5-100%. In aspecific embodiment, fuel 17 comprises 67% methanol by volume.

Fuel processor 15 processes fuel 17 and outputs hydrogen. In oneembodiment, a hydrocarbon fuel processor 15 heats and processes ahydrocarbon fuel 17 in the presence of a catalyst to produce hydrogen.Fuel processor 15 comprises a reformer, which is a catalytic device thatconverts a liquid or gaseous hydrocarbon fuel 17 into hydrogen andcarbon dioxide. As the term is used herein, reforming refers to theprocess of producing hydrogen from a fuel 17. Fuel processor 15 mayoutput either pure hydrogen or a hydrogen bearing gas stream (alsocommonly referred to as ‘reformate’).

Various types of reformers are suitable for use in fuel cell system 10;these include steam reformers, auto thermal reformers (ATR) andcatalytic partial oxidizers (CPOX) for example. A steam reformer onlyneeds steam and fuel to produce hydrogen. ATR and CPOX reformers mix airwith a fuel/steam mixture. ATR and CPOX systems reform fuels such asmethanol, diesel, regular unleaded gasoline and other hydrocarbons. In aspecific embodiment, storage device 16 provides methanol 17 to fuelprocessor 15, which reforms the methanol at about 280° C. or less andallows fuel cell system 10 usage in low temperature applications.

Fuel cell 20 electrochemically converts hydrogen and oxygen to water,generating electrical energy (and sometimes heat) in the process.Ambient air readily supplies oxygen. A pure or direct oxygen source mayalso be used. The water often forms as a vapor, depending on thetemperature of fuel cell 20. For some fuel cells, the electrochemicalreaction may also produce carbon dioxide as a byproduct.

In one embodiment, fuel cell 20 is a low volume ion conductive membrane(PEM) fuel cell suitable for use with portable applications such asconsumer electronics. A PEM fuel cell comprises a membrane electrodeassembly (MEA) that carries out the electrical energy generating anelectrochemical reaction. The MEA includes a hydrogen catalyst, anoxygen catalyst, and an ion conductive membrane that a) selectivelyconducts protons and b) electrically isolates the hydrogen catalyst fromthe oxygen catalyst. A hydrogen gas distribution layer may also beincluded; it contains the hydrogen catalyst and allows the diffusion ofhydrogen therethrough. An oxygen gas distribution layer contains theoxygen catalyst and allows the diffusion of oxygen and hydrogen protonstherethrough. Typically, the ion conductive membrane separates thehydrogen and oxygen gas distribution layers. In chemical terms, theanode comprises the hydrogen gas distribution layer and hydrogencatalyst, while the cathode comprises the oxygen gas distribution layerand oxygen catalyst.

In one embodiment, a PEM fuel cell includes a fuel cell stack having aset of bi-polar plates. In one embodiment, each bi-polar plate is formedfrom a single sheet of metal that includes channel fields on oppositesurfaces of the metal sheet. Thickness for these plates is typicallybelow about 5 millimeters, and compact fuel cells for portableapplications may employ plates thinner than about 2 millimeters. Thesingle bi-polar plate thus dually distributes hydrogen and oxygen: onechannel field distributes hydrogen while a channel field on the oppositesurface distributes oxygen. In another embodiment, each bi-polar plateis formed from multiple layers that include more than one sheet ofmetal.

Multiple bi-polar plates can be stacked to produce the ‘fuel cell stack’in which a membrane electrode assembly is disposed between each pair ofadjacent bi-polar plates. Gaseous hydrogen distribution to the hydrogengas distribution layer in the MEA occurs via a channel field on oneplate while oxygen distribution to the oxygen gas distribution layer inthe MES occurs via a channel field on a second plate on the othersurface of the membrane electrode assembly.

In electrical terms, the anode includes the hydrogen gas distributionlayer, hydrogen catalyst and a bi-polar plate. The anode acts as thenegative electrode for fuel cell 20 and conducts electrons that arefreed from hydrogen molecules so that they can be used externally, e.g.,to power an external circuit or stored in a battery. In electricalterms, the cathode includes the oxygen gas distribution layer, oxygencatalyst and an adjacent bi-polar plate. The cathode represents thepositive electrode for fuel cell 20 and conducts the electrons back fromthe external electrical circuit to the oxygen catalyst, where they canrecombine with hydrogen ions and oxygen to form water.

In a fuel cell stack, the assembled bi-polar plates are connected inseries to add electrical potential gained in each layer of the stack.The term ‘bi-polar’ refers electrically to a bi-polar plate (whethermechanically comprised of one plate or two plates) sandwiched betweentwo membrane electrode assembly layers. In a stack where plates areconnected in series, a bi-polar plate acts as both a negative terminalfor one adjacent (e.g., above) membrane electrode assembly and apositive terminal for a second adjacent (e.g., below) membrane electrodeassembly arranged on the opposite surface of the bi-polar plate.

In a PEM fuel cell, the hydrogen catalyst separates the hydrogen intoprotons and electrons. The ion conductive membrane blocks the electrons,and electrically isolates the chemical anode (hydrogen gas distributionlayer and hydrogen catalyst) from the chemical cathode. The ionconductive membrane also selectively conducts positively charged ions.Electrically, the anode conducts electrons to a load (electrical energyis produced) or battery (energy is stored). Meanwhile, protons movethrough the ion conductive membrane. The protons and used electronssubsequently meet on the cathode side, and combine with oxygen to formwater. The oxygen catalyst in the oxygen gas distribution layerfacilitates this reaction. One common oxygen catalyst comprises platinumpowder thinly coated onto a carbon paper or cloth. Many designs employ arough and porous catalyst to increase surface area of the platinumexposed to the hydrogen and oxygen.

Since the electrical generation process in fuel cell 20 is exothermic,fuel cell 20 may implement a thermal management system to dissipateheat. Fuel cell 20 may also employ a number of humidification plates(HP) to manage moisture levels in the fuel cell.

While the present invention will mainly be discussed with respect to PEMfuel cells, it is understood that the present invention may be practicedwith other fuel cell architectures. The main difference between fuelcell architectures is the type of ion conductive membrane used. Inanother embodiment, fuel cell 20 is phosphoric acid fuel cell thatemploys liquid phosphoric acid for ion exchange. Solid oxide fuel cellsemploy a hard, non-porous ceramic compound for ion exchange and may besuitable for use with the present invention. Generally, any fuel cellarchitecture may be applicable to the fuel processors described hereinthat output hydrogen for a fuel cell. Other such fuel cell architecturesinclude alkaline and molten carbonate fuel cells, for example.

FIG. 1B illustrates schematic operation for the fuel cell system 10 ofFIG. 1A in accordance with a specific embodiment of the presentinvention.

Fuel storage device 16 stores methanol or a methanol mixture as ahydrogen fuel 17. An outlet of storage device 16 includes a connector 23that mates with a mating connector on a package 11. In this case, thepackage 11 includes the fuel cell 20, fuel processor 15, and all otherbalance-of-plant components except the cartridge 16. In a specificembodiment, the connector 23 and mating connector form a quickconnect/disconnect for easy replacement of cartridges 16. The matingconnector communicates methanol 17 into hydrogen fuel line 25, which isinternal to package 11 in this case.

Line 25 divides into two lines: a first line 27 that transports methanol17 to a heater/heater 30 for fuel processor 15 and a second line 29 thattransports methanol 17 for a reformer 32 in fuel processor 15. Lines 25,27 and 29 may comprise channels disposed in the fuel processor (e.g.,channels in metals components) and/or tubes leading thereto.

Flow control is provided on each line 27 and 29. Separate pumps 21 a and21 b are provided for lines 27 and 29, respectively, to pressurize eachline separately and transfer methanol at independent rates, if desired.A model 030SP-S6112 pump as provided by Biochem, NJ is suitable totransmit liquid methanol on either line in a specific embodiment. Adiaphragm or piezoelectric pump is also suitable for use with system 10.A flow restriction may also provided on each line 27 and 29 tofacilitate sensor feedback and flow rate control. In conjunction withsuitable control, such as digital control applied by a processor thatimplements instructions from stored software, each pump 21 responds tocontrol signals from the processor and moves a desired amount ofmethanol 17 from storage device 16 to heater 30 and reformer 32 on eachline 27 and 29. In another specific embodiment shown, line 29 runs inletmethanol 17 across or through a heat exchanger (FIGS. 10A-10C) thatreceives heat from the exhaust of the heater 30 in fuel processor 15.This increases thermal efficiency for system 10 by preheating theincoming fuel (to reduce heating of the fuel in heater 30) andrecuperates heat that would otherwise be expended from the system.

Air source 41 delivers oxygen and air from the ambient room through line31 to the cathode in fuel cell 20, where some oxygen is used in thecathode to generate electricity. Air source 41 may include a pump, fan,blower or compressor, for example. High operating temperatures in fuelcell 20 also heat the oxygen and air.

In the embodiment shown, the heated oxygen and air is then transmittedfrom the fuel cell via line 33 to a regenerator 36 (also referred toherein as a ‘dewar’) of fuel processor 15, where the air is additionallyheated (by the heater, while in the dewar) before entering heater 30.This double pre-heating increases efficiency of the fuel cell system 10by a) reducing heat lost to reactants in heater 30 (such as fresh oxygenthat would otherwise be near room temperature when combusted in theheater), and b) cooling the fuel cell during energy production. In thisembodiment, a model BTC compressor as provided by Hargraves, N.C. issuitable to pressurize oxygen and air for fuel cell system 10.

A fan 37 blows cooling air (e.g., from the ambient room) over fuel cell20. Fan 37 may be suitably sized to move air as desired by heatingrequirements of the fuel cell; and many vendors known to those of skillin the art provide fans suitable for use with package 10.

Fuel processor 15 receives methanol 17 and outputs hydrogen. Fuelprocessor 15 comprises heater 30, reformer 32, boiler 34 and regenerator36. Heater 30 (also referred to herein as a burner when it usescatalytic combustion to generate heat) includes an inlet that receivesmethanol 17 from line 27. In a specific embodiment, the burner includesa catalyst that helps generate heat from methanol. In anotherembodiment, heater 30 also includes its own boiler to preheat fuel forthe heater.

Boiler 34 includes a boiler chamber having an inlet that receivesmethanol 17 from line 29. The boiler chamber is configured to receiveheat from heater 30, via heat conduction through walls in monolithicstructure 100 between the boiler 34 and heater 30, and use the heat toboil the methanol passing through the boiler chamber. The structure ofboiler 34 permits heat produced in heater 30 to heat methanol 17 inboiler 34 before reformer 32 receives the methanol 17. In a specificembodiment, the boiler chamber is sized to boil methanol before receiptby reformer 32. Boiler 34 includes an outlet that provides heatedmethanol 17 to reformer 32.

Reformer 32 includes an inlet that receives heated methanol 17 fromboiler 34. A catalyst in reformer 32 reacts with the methanol 17 toproduce hydrogen and carbon dioxide; this reaction is endothermic anddraws heat from heater 30. A hydrogen outlet of reformer 32 outputshydrogen to line 39. In one embodiment, fuel processor 15 also includesa preferential oxidizer that intercepts reformer 32 hydrogen exhaust anddecreases the amount of carbon monoxide in the exhaust. The preferentialoxidizer employs oxygen from an air inlet to the preferential oxidizerand a catalyst, such as ruthenium that is preferential to carbonmonoxide over hydrogen.

Regenerator 36 pre-heats incoming air before the air enters heater 30.In one sense, regenerator 36 uses outward traveling waste heat in fuelprocessor 15 to increase thermal management and thermal efficiency ofthe fuel processor. Specifically, waste heat from heater 30 pre-heatsincoming air provided to heater 30 to reduce heat transfer to the airwithin the heater. As a result, more heat transfers from the heater toreformer 32. The regenerator also functions as insulation for the fuelprocessor. More specifically, by reducing the overall amount of heatloss from the fuel processor, regenerator 36 also reduces heat loss frompackage 10 by heating air before the heat escapes fuel processor 15.This reduces heat loss from fuel processor 15, which enables cooler fuelcell system 10 packages.

Line 39 transports hydrogen (or ‘reformate’) from fuel processor 15 tofuel cell 20. In a specific embodiment, gaseous delivery lines 33, 35and 39 include channels in a metal interconnect that couples to bothfuel processor 15 and fuel cell 20. A hydrogen flow sensor (not shown)may also be added on line 39 to detect and communicate the amount ofhydrogen being delivered to fuel cell 20. In conjunction with thehydrogen flow sensor and suitable control, such as digital controlapplied by a processor that implements instructions from storedsoftware, fuel processor 15 regulates hydrogen gas provision to fuelcell 20.

Fuel cell 20 includes a hydrogen inlet port that receives hydrogen fromline 39 and includes a hydrogen intake manifold that delivers the gas toone or more bi-polar plates and their hydrogen distribution channels. Anoxygen inlet port of fuel cell 20 receives oxygen from line 31; anoxygen intake manifold receives the oxygen from the port and deliversthe oxygen to one or more bi-polar plates and their oxygen distributionchannels. A cathode exhaust manifold collects gases from the oxygendistribution channels and delivers them to a cathode exhaust port andline 33, or to the ambient room. An anode exhaust manifold 38 collectsgases from the hydrogen distribution channels, and in one embodiment,delivers the gases to the ambient room.

In the embodiment shown, the anode exhaust is transferred back to fuelprocessor 15. In this case, system 10 comprises plumbing 38 thattransports unused hydrogen from the anode exhaust to heater 30. Forsystem 10, heater 30 includes two inlets: an inlet configured to receivefuel 17 and an inlet configured to receive hydrogen from line 38. In oneembodiment, gaseous delivery in line 38 back to fuel processor 15 relieson pressure at the exhaust of the anode gas distribution channels, e.g.,in the anode exhaust manifold. In another embodiment, an anode recyclingpump or fan is added to line 38 to pressurize the line and return unusedhydrogen back to fuel processor 15.

In one embodiment, fuel cell 20 includes one or more heat transferappendages 46 that permit conductive heat transfer with internalportions of a fuel cell stack. In a specific heating embodiment asshown, exhaust of heater 30 in fuel processor 15 is transported to theone or more heat transfer appendages 46 in fuel cell 20 during systemstart-up to expedite reaching initial elevated operating temperatures inthe fuel cell 20. The heat may come from hot exhaust gases or unburnedfuel in the exhaust, which then interacts with a catalyst disposed inproximity to a heat transfer appendage 46. In a specific coolingembodiment, an additional fan 37 blows cooling air over the one or moreheat transfer appendages 46, which provides dedicated and controllablecooling of the stack during electrical energy production.

In addition to the components shown in shown in FIG. 1B, system 10 mayalso include other elements such as electronic controls, additionalpumps and valves, added system sensors, manifolds, heat exchangers andelectrical interconnects useful for carrying out functionality of a fuelcell system 10 that are known to one of skill in the art and omitted forsake of brevity. FIG. 1B shows one specific plumbing arrangement for afuel cell system; other plumbing arrangements are suitable for useherein. For example, the heat transfer appendages 46, a heat exchangerand dewar 36 need not be included. Other alterations to system 10 arepermissible, as one of skill in the art will appreciate.

Fuel processors of the present invention are well suited for use withmicro fuel cell systems. A micro fuel cell system generates dc voltage,and may be used in a wide variety of applications. For example,electrical energy generated by a micro fuel cell may power a notebookcomputer 11 or a portable electrical generator 11 carried by militarypersonnel. In one embodiment, the present invention provides ‘small’fuel cells that are configured to output less than 200 watts of power(net or total). Fuel cells of this size are commonly referred to as‘micro fuel cells’ and are well suited for use with portable electronicsdevices. In one embodiment, the fuel cell is configured to generate fromabout 1 milliwatt to about 200 Watts. In another embodiment, the fuelcell generates from about 5 Watts to about 60 Watts. Fuel cell system 10may be a stand-alone system, which is a single package 11 that producespower as long as it has access to a) oxygen and b) hydrogen or ahydrogen source such as a hydrocarbon fuel. One specific portable fuelcell package produces about 20 Watts or about 45 Watts, depending on thenumber of cells in the stack.

Exemplary Fuel Processor

FIG. 2A illustrates a top perspective view of components included in anexemplary fuel processor 15 in accordance with a specific embodiment ofthe present invention. FIG. 2B illustrates a cross-sectional front viewof a central portion of fuel processor 15. Fuel processor 15 reformsmethanol to produce hydrogen. Fuel processor 15 includes monolithicstructure 100, end plates 182 and 184, end plate 185, reformer 32,heater 30, boiler 34, boiler 108, dewar 150 and housing 152. Althoughthe present invention will now be described with respect to methanolconsumption for hydrogen production, it is understood that fuelprocessors of the present invention may consume another fuel, such asone of the fuels listed above.

Referring initially to FIG. 2B, monolithic structure 100 includesreformer 32, heater 30, boiler 34 and boiler 108. As the term is usedherein, ‘monolithic’ refers to a single and integrated structure. Thestructure may include one or more materials that permit conductive heattransfer within the fuel processor. Monolithic structure 100 comprises asingle material 141, where cavities and space in the material 141 formreformer 32, heater 30, boiler 34 and boiler 108. The monolithicstructure 100 and common material 141 simplify manufacture of fuelprocessor 15. For example, using a metal for common material 141 allowsmonolithic structure 100 to be formed by extrusion to shape reformer 32,heater 30, boiler 34 and boiler 108. In a specific embodiment,monolithic structure 100 is consistent in cross sectional dimensionsbetween end plates 182 and 184 and solely comprises copper or anothermetal that has been formed in a single extrusion.

Outside monolithic structure 100, fuel processor 15 includes plumbinginlets and outlets for reformer 32, heater 30 and boiler 34 disposed onend plates 182 and 184 and interconnect 190, which will be described infurther detail below.

Housing 152 (FIG. 3B) provides mechanical protection for internalcomponents of fuel processor 15 such as monolithic structure 100.Housing 152 also provides separation from the environment external toprocessor 15 and may include inlet and outlet ports for gaseous andliquid communication in and out of fuel processor 15. In this case,housing 152 includes a set of walls that at least partially contain adewar 150. The housing walls may include a suitably stiff material suchas a metal or a rigid polymer, for example.

Boiler 34 pre-heats methanol for reformer 32. Boiler 34 receivesmethanol via a fuel inlet on interconnect 190, which couples to amethanol supply line 27 (FIG. 1B). Since methanol reforming and hydrogenproduction via a catalyst 102 in reformer 32 often requires elevatedmethanol temperatures, fuel processor 15 pre-heats the methanol beforereceipt by reformer 32 via boiler 34. As shown in the cross section ofFIG. 2B, boiler 34 is disposed in proximity to heater 30 to receive heatgenerated in heater 30. The heat transfers via conduction throughmaterial 141 in monolithic structure 100 from heater 30 to boiler 34 andvia convection from boiler 34 walls to the methanol passingtherethrough. In one embodiment, boiler 34 is configured to vaporizeliquid methanol. Boiler 34 then passes the gaseous methanol to reformer32 for gaseous interaction with catalyst 102.

Reformer 32 is configured to receive methanol from boiler 34. Internalwalls in monolithic structure 100 and end walls on end plates 182 and184 define dimensions for one or more reformer chambers 103. In oneembodiment, end plate 182 and/or end plate 184 includes a channel thatroutes heated methanol exhausted from boiler 34 into reformer 32.

In one embodiment, a reformer includes a multi-pass arrangement that hasmultiple reformer chambers 103. As shown in FIGS. 2A and 2B, reformer 32includes three multi-pass chambers that process methanol in series.Reformer 32 then includes the volume of all three chambers 103 a-c. Eachchamber traverses the length of monolithic structure 100, and opens toeach other in series such that chambers 103 a-c form one contiguous pathfor gaseous flow. More specifically, heated and gaseous methanol fromboiler 34 a) enters reformer chamber 103 a at an inlet end of monolithicstructure 100 and flows to the other end of structure 100 and overcatalyst 102 in chamber 103 a, b) then flows into second reformerchamber 103 b at the second end of monolithic structure 100 and flowsover catalyst 102 in chamber 103 b from one end of monolithic structure100 to the other, and c) flows into reformer chamber 103 c at one end ofmonolithic structure 100 and flows to the other end over catalyst 102 inchamber 103 c.

Reformer 32 includes a catalyst 102 that facilitates the production ofhydrogen. Catalyst 102 reacts with methanol and produces hydrogen gasand carbon dioxide. In one embodiment, catalyst 102 comprises pelletspacked to form a porous bed or otherwise suitably filled into the volumeof reformer chambers 103. Pellet diameters ranging from about 50 micronsto about 1.5 millimeters are suitable for many applications. Pelletdiameters ranging from about 500 microns to about 1 millimeter aresuitable for use with reformer 32. One suitable catalyst 102 may includeCuZn coated onto alumina pellets when methanol is used as a hydrocarbonfuel 17. Other materials suitable for catalyst 102 include platinum,palladium, a platinum/ palladium mix, nickel, and other precious metalcatalysts for example. Catalyst 102 pellets are commercially availablefrom a number of vendors known to those of skill in the art. Catalyst102 may also comprise catalyst materials listed above coated onto ametal sponge or metal foam. A wash coat of the desired metal catalystmaterial onto the walls of reformer chamber 103 may also be used withreformer 32.

Reformer 32 is configured to output hydrogen and includes an outlet port191 (FIG. 2A) that communicates hydrogen produced in reformer 32 outsideof fuel processor 15. Port 191 is disposed on a wall of end plate 184and includes a hole that passes through the wall. Port 191 opens tohydrogen line in interconnect 190, which then forms part of a hydrogenprovision line 39 (FIG. 1B) for transfer of the hydrogen to fuel cell 20for electrical energy generation.

Hydrogen production in reformer 32 is slightly endothermic and drawsheat from heater/heater 30. In the embodiment shown, heater 30 employscatalytic combustion to generate heat. As the term is used herein, aburner refers to a heater that uses a catalytic process to produce heat.A heater refers to any mechanism or system for producing heat in a fuelprocessor. A fuel processor of the present invention may alternativelyemploy an electrical mechanism that, for example, uses electricalresistance and electrical energy to produce heat. Although fuelprocessor 15 is mainly discussed with respect to a chemical-basedheater/heater 30, the fuel processor may alternatively include othersources of heat.

As shown in FIG. 2B, catalytic heater 30 comprises four burner chambers105 a-d that surround reformer 32 in cross section. A catalyst 104disposed in each burner chamber 105 helps a burner fuel passed throughthe chamber generate heat. Heater 30 includes an inlet that receivesmethanol 17 from boiler 108 via a channel in one of end plates 182 or184. In one embodiment, methanol produces heat in heater 30 and catalyst104 facilitates the methanol production of heat. In another embodiment,waste hydrogen from fuel cell 20 produces heat in the presence ofcatalyst 104. Suitable burner catalysts 104 may include platinum orpalladium coated onto alumina pellets for example. Other materialssuitable for catalyst 104 include iron, tin oxide, other noble-metalcatalysts, reducible oxides, and mixtures thereof. Catalyst 104 iscommercially available from a number of vendors known to those of skillin the art as small pellets. The pellets may be packed into burnerchamber 105 to form a porous bed or otherwise suitably filled into theburner chamber volume. Catalyst 104 pellet sizes may be varied relativeto the cross sectional size of burner chamber 105. Catalyst 104 may alsocomprise catalyst materials listed above coated onto a metal sponge ormetal foam or wash coated onto the walls of burner chamber 105.

Some fuels generate additional heat in heater 30 or generate heat moreefficiently with elevated temperatures. Fuel processor 15 includes aboiler 108 that heats methanol before heater 30 receives the fuel.Boiler 108 is disposed in proximity to heater 30 to receive heatgenerated in heater 30; the heat transfers via conduction throughmonolithic structure 100 from heater 30 to boiler 108 and via convectionfrom boiler 108 walls to the methanol passing therethrough.

Air including oxygen enters fuel processor 15 via an air inlet port 191in interconnect 190. Heater 30 uses the oxygen for catalytic combustionof methanol.

Heater 30 typically operates at an elevated temperature. In oneembodiment, fuel processor 15 comprises a dewar 150 to improve thermalmanagement for fuel processor 15. Dewar 150 at least partially thermallyisolates components internal to housing 152—such as heater 30—andcontains heat within fuel processor 15. Dewar 150 is shaped and sized toform two sets of air chambers/channels: a first air chamber 156 betweenthe outside of monolithic structure 100 and the inside of dewar 150; anda second air chamber 158 between the outside of dewar 150 and the insideof housing 152. The chambers 156 and 158 include spaces for airflow andregenerative cooling. More specifically, dewar 150 is configured suchthat air passing through dewar chambers 156 and 158 receives heatgenerated in heater 30. Air is routed through one or both channels 156and 158 to improve thermal heat management for fuel processor 15 by: a)allowing incoming air to be pre-heated before entering heater 30, and b)dissipating waste heat generated by burner 32 into the incoming airbefore the heat reaches the outside of housing 152. Dewar 150 offersthus two functions for fuel processor 15: a) it permits active coolingof components of fuel processor 15 before the heat reaches an outerportion of the fuel processor, and b) it pre-heats the air going toheater 30 to improve thermal efficiency.

In one embodiment, the fuel cell system runs anode exhaust from the fuelcell 20 back to fuel processor. As shown in FIG. 1B, line 38 routesunused hydrogen from fuel cell 20 to a burner inlet, which provides theanode exhaust to heater 30 (or to the regenerator 36 and then to burnerinlet 109 and into heater 30). Heater 30 includes a thermal catalystthat reacts with the unused hydrogen to produce heat. Since hydrogenconsumption within a PEM fuel cell 20 is often incomplete and the anodeexhaust often includes unused hydrogen, re-routing the anode exhaust toheater 30 allows a fuel cell system to capitalize on unused hydrogen andincrease hydrogen usage and energy efficiency. The fuel cell system thusprovides flexibility to use different fuels in a catalytic heater 30.For example, if fuel cell 20 can reliably and efficiently consume over90% of the hydrogen in the anode stream, then there may not besufficient hydrogen to maintain reformer and boiler operatingtemperatures in fuel processor 15. Under this circumstance, methanolsupply is increased to produce additional heat to maintain the reformerand boiler temperatures.

Burner inlet 109 traverses monolithic structure 100 and carries anodeexhaust from fuel cell 20 before provision into heater 30. Disposingburner inlet 109 adjacent to a burner chamber 105 also heats theincoming anode exhaust, which reduces heat transferred to the anodeexhaust within the burner chambers 105.

A fuel cell package may include other fuel processor designs. Manyarchitectures employ a planar reformer disposed on top or below to aplanar burner. Micro-channel designs fabricated in silicon that commonlyemploy such stacked planar architectures may be used. Other fuelprocessors may be used that process fuels other than methanol. Fuelsother than methanol were listed above, and processors for these fuelsare not detailed herein for sake of brevity.

Interconnect 190 is disposed at least partially between fuel cell 20 andfuel processor 15, and forms a structural and plumbing intermediarybetween the two. One or more conduits traverse interconnect 190 andpermit gaseous and/or fluid communication between the fuel cell and thefuel processor. The interconnect 190 also reduces plumbing complexityand space, which leads to a smaller fuel cell system package. Theinterconnect 190 includes a set of conduits, formed in the structure ofthe interconnect 190, that each communicate a liquid or gas between thefuel processor and the fuel cell.

Interconnect 190 may include one or more materials. In one embodiment,interconnect 190 is constructed from a suitably rigid material that addsstructural integrity to a fuel cell package and provides rigidconnectivity between a fuel cell and fuel processor. Many metals aresuitable for use with interconnect 190.

Interconnect 190 includes plumbing for communicating any number of gasesand liquids between a fuel cell and fuel processor. For the fuel cellsystem 10 of FIG. 1B, plumbing serviced by interconnect 190 includes 1)a hydrogen line 39 from the fuel processor to the fuel cell, 2) a line38 returning unused hydrogen from the fuel cell back to the fuelprocessor, 3) an oxygen line 33 from the fuel cell to the fuelprocessor, and 4) a reformer or burner exhaust line 37 traveling fromthe fuel processor to the fuel cell. Other gas or liquid transfersbetween a fuel cell and fuel processor, in either direction, may beserviced by interconnect 190. In one embodiment, interconnect 190internally incorporates all plumbing for gases and liquids it transfersto minimize exposed tubing and package size.

Fuel Cell

FIG. 3A illustrates a simplified cross sectional view of a fuel cellstack 60 for use in fuel cell 20 in accordance with one embodiment ofthe present invention. FIG. 3B illustrates an outer top perspective viewof a fuel cell stack 60 and fuel cell 20 in accordance with anotherembodiment of the present invention.

Referring initially to FIG. 3A, fuel cell stack 60 includes a set ofbi-polar plates 44 and a set of membrane electrode assembly (MEA) layers62. Two MEA layers 62 neighbor each bi-polar plate 44. With theexception of topmost and bottommost membrane electrode assembly layers62 a and 62 b, each MEA 62 is disposed between two adjacent bi-polarplates 44. For MEAs 62 a and 62 b, top and bottom end plates 64 a and 64b include a channel field 72 on the face neighboring an MEA 62.

The bi-polar plates 44 in stack 60 also each include one or more heattransfer appendages 46. As shown, each bi-polar plate 44 includes a heattransfer appendage 46 a on one side of the plate and a heat transferappendage 46 b on the opposite side. Heat transfer appendages 46 arediscussed in further detail below.

The number of bi-polar plates 44 and MEA layers 62 in each set may varywith design of fuel cell stack 60. Stacking parallel layers in fuel cellstack 60 permits efficient use of space and increased power density forfuel cell 20 and a fuel cell package 10 including fuel cell 20. In oneembodiment, each membrane electrode assembly 62 produces 0.7 V and thenumber of MEA layers 62 is selected to achieve a desired voltage. Fuelcell 20 size and layout may also be tailored and configured to output agiven power.

Referring to FIG. 3B, top and bottom end plates 64 a and 64 b providemechanical protection for stack 60. End plates 64 also hold the bi-polarplates 44 and MEA layers 62 together, and apply pressure across theplanar area of each bi-polar plate 44 and each MEA 62. End plates 64 mayinclude steel or another suitably stiff material. Bolts 82 a-d connectand secure top and bottom end plates 64 a and 64 b together.

Fuel cell 20 includes two anode manifolds (84 and 86). Each manifolddelivers a product or reactant gas to or from the fuel cell stack 60.More specifically, each manifold delivers a gas between a verticalmanifold created by stacking bi-polar plates 44 (FIG. 3C) and plumbingexternal to fuel cell 20. Inlet hydrogen manifold 84 is disposed on topend plate 64 a, couples with an inlet conduit to receive hydrogen gas,and opens to an inlet hydrogen manifold 102 (FIG. 3C) that is configuredto deliver inlet hydrogen gas to a channel field 72 on each bi-polarplate 44 in stack 60. Outlet manifold 86 receives outlet gases from ananode exhaust manifold 104 (FIG. 3C) that is configured to collect wasteproducts from the anode channel fields 72 of each bi-polar plate 44.Outlet manifold 86 may provide the exhaust gases to the ambient spaceabout the fuel cell. In another embodiment, manifold 86 provides theanode exhaust to line 38, which transports the unused hydrogen back tothe fuel processor during start-up.

Fuel cell 20 includes two cathode manifolds: an inlet cathode manifoldor inlet oxygen manifold 88, and an outlet cathode manifold or outletwater/vapor manifold 90. Inlet oxygen manifold 88 is disposed on top endplate 64 a, couples with an inlet conduit (conduit 31, which draws airfrom the ambient room) to receive ambient air, and opens to an oxygenmanifold 106 (FIG. 3C) that is configured to deliver inlet oxygen andambient air to a channel field 72 on each bi-polar plate 44 in stack 60.Outlet water/vapor manifold 90 receives outlet gases from a cathodeexhaust manifold 108 (FIG. 3C) that is configured to collect water(typically as a vapor) from the cathode channel fields 72 on eachbi-polar plate 44.

As shown in FIG. 3B, manifolds 84, 86, 88 and 90 include molded channelsthat each travel along a top surface of end plate 64 a from theirinterface from outside the fuel cell to a manifold in the stack. Eachmanifold or channel acts as a gaseous communication line for fuel cell20 and may comprise a molded channel in plate 64 or a housing of fuelcell 20. Other arrangements to communicate gases to and from stack 60are contemplated, such as those that do not share common manifolding ina single plate or structure.

In one embodiment, fuel cell 20 requires no external humidifier or heatexchanger and the stack 60 only needs hydrogen and air to produceelectrical power. Alternatively, fuel cell 20 may employ humidificationof the cathode to fuel cell 20 improve performance. For some fuel cellstack 60 designs, humidifying the cathode increases the power andoperating life of fuel cell 20.

FIG. 3C illustrates a top perspective view of a stack of bi-polar plates(with the top two plates labeled 44 p and 44 q) in accordance with oneembodiment of the present invention. Bi-polar plate 44 is a single plate44 with first channel fields 72 disposed on opposite faces 75 of theplate 44.

Functionally, bi-polar plate 44 a) delivers and distributes reactantgases to the gas diffusion layers 122 and 124 and their respectivecatalysts, b) maintains separation of the reactant gasses from oneanother between MEA layers 62 in stack 60, c) exhausts electrochemicalreaction byproducts from MEA layers 62, d) facilitates heat transfer toand/or from MEA layers 62 and fuel cell stack 60, and e) includes gasintake and gas exhaust manifolds for gas delivery to other bi-polarplates 44 in the fuel stack 60.

Bi-polar plate 44 includes a channel field 72 or “flow field” on eachface of plate 44. Each channel field 72 includes one or more channels 76formed into the substrate 89 of plate 44 such that the channel restsbelow the surface of plate 44. Each channel field 72 distributes one ormore reactant gasses to an active area for the fuel cell stack 60. Forfuel cell stack 60, each channel field 72 is configured to receive areactant gas from an intake manifold 102 or 106 and configured todistribute the reactant gas to a gas diffusion layer 122 or 124. Eachchannel field 72 also collects reaction byproducts for exhaust from fuelcell 20.

Bi-polar plate 44 may include one or more heat transfer appendages 46.Each heat transfer appendage 46 permits external thermal management ofinternal portions of fuel cell stack 60. More specifically, appendage 46may be used to heat or cool internal portions of fuel cell stack 60 suchas internal portions of each attached bi-polar plate 44 and anyneighboring MEA layers 62, for example. Heat transfer appendage 46 islaterally arranged outside channel field 72. In one embodiment,appendage 46 is disposed on an external portion of bi-polar plate 44.External portions of bi-polar plate 44 include any portions of plate 44proximate to a side or edge of the substrate included in plate 44.External portions of bi-polar plate 44 typically do not include achannel field 72. For the embodiment shown, heat transfer appendage 46substantially spans a side of plate 44 that does not include intake andoutput manifolds 102-108. For the embodiment shown in FIG. 2A, plate 44includes two heat transfer appendages 46 that substantially span bothsides of plate 44 that do not include a gas manifold.

Peripherally disposing heat transfer appendage 46 allows heat transferbetween inner portions of plate 44 and the externally disposed appendage46 via the plate substrate 89. Conductive thermal communication refersto heat transfer between bodies that are in contact or that areintegrally formed. Thus, lateral conduction of heat between externalportions of plate 44 (where the heat transfer appendage 46 attaches) andcentral portions of bi-polar plate 44 occurs via conductive thermalcommunication through substrate 89. In one embodiment, heat transferappendage 46 is integral with substrate material 89 in plate 44.Integral in this sense refers to material continuity between appendage46 and plate 44. An integrally formed appendage 46 may be formed withplate 44 in a single molding, stamping, machining or MEMs process of asingle metal sheet, for example. Integrally forming appendage 46 andplate 44 permits conductive thermal communication and heat transferbetween inner portions of plate 44 and the heat transfer appendage 46via substrate 89. In another embodiment, appendage 46 comprises amaterial other than that used in substrate 89 that is attached ontoplate 44 and conductive thermal communication and heat transfer occursat the junction of attachment between the two attached materials.

Heat may travel to or form the heat transfer appendage 46. In otherwords, appendage 46 may be employed as a heat sink or source. Thus, heattransfer appendage 46 may be used as a heat sink to cool internalportions of bi-polar plate 44 or an MEA 62. Fuel cell 20 employs acooling medium to remove heat from appendage 46. Alternatively, heattransfer appendage 46 may be employed as a heat source to provide heatto internal portions of bi-polar plate 44 or an MEA 62. In this case, acatalyst may be disposed on appendage 46 to generate heat in response tothe presence of a heating medium.

For cooling, heat transfer appendage 46 permits integral conductive heattransfer from inner portions of plate 44 to the externally disposedappendage 46. During hydrogen consumption and electrical energyproduction, the electrochemical reaction generates heat in each MEA 62.Since internal portions of bi-polar plate 44 are in contact with the MEA62, a heat transfer appendage 46 on a bi-polar plate 44 thus cools anMEA 62 adjacent to the plate via a) conductive heat transfer from MEA 62to bi-polar plate 44 and b) lateral thermal communication and conductiveheat transfer from central portions of the bi-polar plate 44 in contactwith the MEA 62 to the external portions of plate 44 that includeappendage 46. In this case, heat transfer appendage 46 sinks heat fromsubstrate 89 between a first channel field 72 on one face 75 of plate 44and a second channel field 72 on the opposite face of plate 44 to heattransfer appendage 46 in a direction parallel to a face 75 of plate 44.When a fuel cell stack 60 includes multiple MEA layers 62, lateralthermal communication through each bi-polar plate 44 in this mannerprovides interlayer cooling of multiple MEA layers 62 in stack 60 —including those layers in central portions of stack 60.

Fuel cell 20 may employ a cooling medium that passes over heat transferappendage 46. The cooling medium receives heat from appendage 46 andremoves the heat from fuel cell 20. Heat generated internal to stack 60thus conducts through bi-polar plate 44, to appendage 46, and heats thecooling medium via convective heat transfer between the appendage 46 andcooling medium. Air is suitable for use as the cooling medium.

Heat transfer appendage 46 may be configured with a thickness that isless than the thickness between opposite faces 75 of plate 44. Thereduced thickness of appendages 46 on adjacent bi-polar plates 44 in thefuel cell stack 60 forms a channel between adjacent appendages. Multipleadjacent bi-polar plates 44 and appendages 46 in stack form numerouschannels. Each channel permits a cooling medium or heating medium topass therethrough and across heat transfer appendages 46. In oneembodiment, fuel cell stack 60 includes a mechanical housing thatencloses and protects stack 60. Walls of the housing also provideadditional ducting for the cooling or heating medium by forming ductsbetween adjacent appendages 46 and the walls.

The cooling medium may be a gas or liquid. Heat transfer advantagesgained by high conductance bi-polar plates 44 allow air to be used as acooling medium to cool heat transfer appendages 46 and stack 60. Forexample, fan 37 of FIG. 1B moves air through the mechanical housing,through the channels between appendages to cool heat transfer appendages46 and fuel cell stack 60, and out an exhaust hole or port in themechanical housing. Fuel cell system 10 may then include active thermalcontrols based on temperature feedback. Increasing or decreasing coolantfan speed regulates the amount of heat removal from stack 60 and theoperating temperature for stack 60. In one embodiment of an air-cooledstack 60, the coolant fan speed increases or decreases as a function ofthe actual cathode exit temperature, relative to a desired temperatureset-point.

For heating, heat transfer appendage 46 allows integral heat transferfrom the externally disposed appendage 46 to inner portions of plate 44and any components and portions of fuel cell 20 in thermal communicationwith inner portions of plate 44. A heating medium passed over the heattransfer appendage 46 provides heat to the appendage. Heat convectedonto the appendage 46 then conducts through the substrate 89 and intointernal portions of plate 44 and stack 60, such as portions of MEA 62and its constituent components.

Although the present invention provides a bi-polar plate 44 havingchannel fields 72 that distribute hydrogen and oxygen on opposing sidesof a single plate 44, many embodiments described herein are suitable foruse with conventional bi-polar plate assemblies that employ two separateplates for distribution of hydrogen and oxygen.

While the present invention has mainly been discussed so far withrespect to a reformed methanol fuel cell (RMFC), the present inventionmay also apply to other types of fuel cells, such as a solid oxide fuelcell (SOFC), a phosphoric acid fuel cell (PAFC), a direct methanol fuelcell (DMFC), or a direct ethanol fuel cell (DEFC). In this case, fuelcell 20 includes components specific to these architectures, as one ofskill in the art will appreciate. A DMFC or DEFC receives and processesa fuel. More specifically, a DMFC or DEFC receives liquid methanol orethanol, respectively, channels the fuel into the fuel cell stack 60 andprocesses the liquid fuel to separate hydrogen for electrical energygeneration. For a DMFC, channel fields 72 in the bi-polar plates 44distribute liquid methanol instead of hydrogen. Hydrogen catalyst 126described above would then comprise a suitable anode catalyst forseparating hydrogen from methanol. Oxygen catalyst 128 would comprise asuitable cathode catalyst for processing oxygen or another suitableoxidant used in the DMFC, such as peroxide. In general, hydrogencatalyst 126 is also commonly referred to as an anode catalyst in otherfuel cell architectures and may comprise any suitable catalyst thatremoves hydrogen for electrical energy generation in a fuel cell, suchas directly from the fuel as in a DMFC. In general, oxygen catalyst 128may include any catalyst that processes an oxidant in used in fuel cell20. The oxidant may include any liquid or gas that oxidizes the fuel andis not limited to oxygen gas as described above. An SOFC, PAFC or MCFCmay also benefit from inventions described herein, for example. In thiscase, fuel cell 20 comprises an anode catalyst 126, cathode catalyst128, anode fuel and oxidant according to a specific SOFC, PAFC or MCFCdesign.

Heat Efficient Systems

The present invention improves thermal efficiency of a fuel cell system.In one embodiment, a fuel cell system runs a heating medium to the fuelcell to heat the fuel cell.

The heating medium may include any hot gas, a fuel processed in the fuelcell system to make hydrogen (after processing and without anyprocessing), a dedicated heating medium for heating the fuel cell,and/or hydrogen for example. Other suitable heating mediums include anyheated gases emitted from fuel processor 15, or heated via a heatexchanger that receives heat from fuel processor 15 and/or fuel cell 20,for example.

Dedicated plumbing transports the heating medium to the fuel cell or aspecific portion of the fuel cell. For example, in the design shown inFIG. 1B, line 35 transports heated gases to fan 37, which moves theheated gases over the fuel cell stack and heat transfer appendages 46.In this case, line 35 may continue through the fuel cell housing andopen in the proximity of one or more heat transfer appendages. Inanother embodiment, the heating medium is passed to a thermal catalystthat is remote from the fuel cell, and a heat transfer pipe conducts theheat to the fuel cell. As the term is used herein, plumbing may compriseany tubing, piping and/or channeling (e.g., in interconnect 190 anddedicated channels in the fuel cell) that communicates a gas or liquidfrom one location to a second location. The plumbing may also compriseone or more valves, gates or other devices to facilitate and controlflow.

In one embodiment, the heating medium comprises a heated gas having atemperature greater than that of the fuel cell or heat transferappendage 46. Exhaust gases from heater 30 or reformer 32 of fuelprocessor 15 may each include elevated temperatures that are suitablefor heating. A catalytic burner or electrical resistance heater alsooperates at elevated temperatures and produced hot gases. Air exhaustedfrom an electric heater chamber or a catalytic burner chamber is oftengreater than about 100 degrees Celsius. For many catalytic burners,depending on the fuel employed, the heating medium is commonly greaterthan about 200 degrees Celsius when the heating medium leaves the fuelprocessor. In one embodiment, the reformer exhaust is at an elevatedtemperature corresponding to the temperature in reformer 32 and theheating medium includes hot gases. Reformer exhausts above 100 degreesCelsius are common. The heated gases are transported to the fuel cellfor convective heat transfer to the fuel cell, such as passing theheated gases over one or more heat transfer appendages 46 for convectiveheat transfer from the warmer gases into the cooler heat transferappendages and/or to the walls of the fuel cell. Heat then conducts fromthese external portions into the fuel stack and its internal components,such as the MEAs.

The heating medium may also rely on catalytic interaction to generateheat. Fuel cell 20 then comprises a thermal catalyst that facilitatesproduction of heat in the fuel cell in the presence of the heatingmedium. As one of skill in the art will appreciate, the particularcatalyst and heating medium used may vary (e.g. with the fuel cellsystem and its inlet fuel and operating temperatures) but will generallycorrespond to each other. Suitable catalysts for methanol, such asplatinum or palladium coated onto alumina pellets, are described abovewith respect to catalyst 104 in heater 30. Other suitable methanolcatalysts 192 include a platinum/ palladium mix, iron, ruthenium, andcombinations thereof. Each of these will react with methanol and otherhydrocarbon fuels to generate heat. For catalytic heat generation infuel cell 20, the plumbing transports the heating medium to facilitategaseous interaction with the catalyst.

In one embodiment, the fuel cell comprises a catalyst (e.g., catalyst192 of FIG. 3A) disposed in contact with, or in proximity to, one ormore heat transfer appendages 46. The catalyst 192 generates heat whenthe heating medium passes over it. The heating medium in this case maycomprise any gas or fluid that reacts with catalyst 192 to generateheat. Typically, catalyst 192 and the heating medium employ anexothermic chemical reaction to generate heat. Heat transfer appendage46 and plate 44 then conduct heat into the fuel cell stack 60, e.g. toheat internal MEA layers 62.

For example, catalyst 192 may comprise platinum and the heating mediumincludes fuel 17. The methanol 17 is heated to a gaseous state before itenters fuel cell 20 (e.g., in the burner or reformer). This allowsgaseous transportation of the heating medium and gaseous interactionbetween fuel 17 and catalyst 192 to generate heat. A fan, for example,disposed on one of the walls then moves the gaseous methanol within fuelcell 20 and over the catalyst 192.

In one embodiment, the heating medium includes fuel 17 from storagedevice 16. Three suitable routes for the fuel to reach the fuel cell(for heating) include: a) heater 30 exhaust, b) reformer 32 exhaust,and/or c) a dedicated line that communicates the fuel 17 directly fromthe storage device 16 to the fuel cell for catalytic heating.

FIG. 1B shows plumbing that communicates gaseous output of the heater 30to fuel cell 20. In this case, heater 30 is a catalytic burner and theheating medium comprises the fuel 17. Catalytic combustion in heater 30is often incomplete and the burner exhaust gases include unused andgaseous methanol. Line 35 transports the unused methanol to a thermalcatalyst in fuel cell 20. This efficiently uses any fuel remaining inthe burner exhaust to heat the fuel cell 20.

FIG. 4 shows another embodiment of the invention where reformer exhaustis passed to fuel cell 20 for heating. Line 39 splits into two lines:line 39 a that communicates reformate to a hydrogen intake manifold infuel cell 20, and line 39 b that communicates the reformate to fuel cell20 for heating. A valve is disposed at the junction of line 39 a and 39b and controls which path the reformate takes. Line 39 b may alsotransport the reformer exhaust to fan 37, which moves the heating mediumwithin fuel cell 20 and across the heat transfer appendages.

Hydrogen production in reformer 32 is often incomplete and the reformerexhaust/heating medium includes unprocessed and gaseous methanol. Thisis typical during system start-up before the fuel processor and/or fuelcell has reached their respective operating temperatures and thereformer exhaust gases include unprocessed methanol in the reformate.Fuel cell 20 then comprises a thermal catalyst that facilitatesproduction of heat in the fuel cell in the presence of methanol. Boiler34 vaporizes the methanol prior to reaching reformer 32. In this case,line 39 b transports the gaseous methanol and reformate to the thermalcatalyst in fuel cell 20. Suitable methanol catalysts, such as platinumor palladium coated onto alumina pellets, were also described above withrespect to burner 30 of FIG. 30. This embodiment efficiently uses anyunprocessed fuel remaining in the reformer exhaust (after hydrogenprocessing in fuel processor 15) to heat the fuel cell.

In another embodiment, a fuel cell system of the present inventionincludes a separate and dedicated fuel feed that directly supplies fuel17 to fuel cell 20 for heating and reaction with a thermal catalyst. Aseparate pump then controls fuel flow along this line for heatingpurposes.

The fuel is typically vaporized prior to reaching the catalyst tofacilitate transportation and catalytic interaction. A separate fuelline that communicates fuel from the cartridge may employ a designatedelectrical heater configured to vaporize the fuel. The reformer andburner routes already vaporize the fuel in the fuel processor, whichefficiently and doubly uses heat from heater 30 to pre-heat fuel a) inthe fuel processor and b) traveling to fuel cell 20 for heating.

Hydrogen may also be used as a heating medium. In a specific embodiment,the thermal catalyst is configured to interact with hydrogen output fromthe reformer or fuel cell. Reformer hydrogen is particularly usefulduring start-up before hydrogen concentration in the reformate hasreached an acceptable level for use in the fuel cell (the fuel processorhas not warmed up yet), or the fuel cell has not reached an operatingtemperature. When hydrogen is used as the heating medium, catalyst 192includes a material that generates heat in the presence of hydrogen,such as palladium or platinum. In another embodiment, the anode exhaustis transported to the thermal catalyst to heat the fuel cell usinghydrogen that was not processed in the fuel cell 20.

Heating may occur at various times. In one embodiment, the heatingmedium is transported to the fuel cell during a start-up period beforethe fuel cell reaches an operating temperature or before the fuel cellbegins generating electrical energy, e.g., in response to a request forelectrical energy by an electronics device powered by the fuel cell.Heating a fuel cell in this manner allows fuel cell components, such asthe MEA, to reach operating temperatures sooner—and thus expeditesstart-up for the fuel cell system and expedites initial delivery ofelectrical energy.

In another embodiment, the heating medium is transported from the fuelprocessor to the fuel cell during a period of non-activity in which thefuel cell does not generate electrical energy and a component of thefuel cell cools below its operating temperature. Since many fuel cellsrequire elevated temperatures for operation and the electrical energygenerating process is exothermic, the fuel cell usually does not requireexternal heating during electrical energy generation. However, whenelectrical generation ceases for an extended time and one or morecomponents cool below a threshold operating temperature, the heatingmedium may then be transported from the fuel processor to the fuel cellto regain the operating temperature and resume electrical energygeneration sooner. This also permits operating temperatures in a fuelcell to be maintained when electrical energy is not being generated bythe fuel cell, thus allowing electrical energy to be generated instantlyupon request (e.g., a system standby mode in which the fuel cell remainsat operating temperature, despite no continuous request forelectricity).

The thermal catalyst may be flexibly located in the system. Many fuelcell systems of the present invention are provided in portable packages.In general, the catalyst can be located anywhere in the package. As willbe described below, a heat transfer pipe between the thermal catalystand fuel cell permits the catalyst to be separated from the fuel cell inthe package.

In one embodiment, the catalyst is disposed close enough to the fuelcell such that catalytic heat conductively transfers from the catalystdirectly to the fuel cell cell. As shown in FIG. 3A, catalyst 192 isarranged on, and in contact with, each heat transfer appendage 46. Inthis case, the heating medium passes over each appendage 46 and reactswith thermal catalyst 192. This generates heat, which is absorbed viaconductive thermal communication by the cooler appendage 46.

Wash coating may be employed to dispose catalyst 192 on each appendage46. A ceramic support may also be used to bond catalyst 192 on anappendage 46. In a specific embodiment, the plumbing delivers theheating medium to one or more bulkheads that contain the catalystproximate to the fuel cell or heat transfer appendages 46. The bulkheadrefers to any closed space used to contain a thermal catalyst, andseveral examples are described below with respect to FIGS. 5A-5C.Additional catalyst arrangements are described in commonly owned andco-pending patent application Ser. No. 10/877,771 and entitled“EFFICIENT MICRO FUEL CELL SYSTEMS AND METHODS”, which was incorporatedby reference above.

Still referring to FIG. 3A, the heat transfers into fuel cell 20 via thefuel cell walls and/or one or more heat transfer appendages 46. Forcatalyst-based heating using a thermal catalyst disposed in proximity toa heat transfer appendage, heat then a) transfers from catalyst 192 toappendage 46, b) transfers laterally though bi-polar plate 44 viaconductive heat transfer from outer lateral portions of the plate thatinclude heat transfer appendage 46 to central portions of bi-polar plate44 in contact with the MEA layers 62, and c) conducts from bi-polarplate 44 to MEA layer 62. When a fuel cell stack 60 includes multipleMEA layers 62, lateral heating through each bi-polar plate 44 providesinterlayer heating of multiple MEA layers 62 in internal portions ofstack 60, including the x-y-z central and hard to reach volume portions,which expedites fuel cell 20 warm up.

Bi-polar plates 44 of FIG. 3A include heat transfer appendages 46 oneach side. In a specific embodiment, one set of heat transfer appendages46 a is used for cooling while the other set of heat transfer appendages46 b is used for heating. Alternatively, the same appendages may be usedfor heating and cooling. Or multiple appendages may be used for heating.Bi-polar plates 44 illustrated in FIG. 3C show plates 44 with four heattransfer appendages 46 disposed on three sides of stack 60, all of whichmay be used for heating and/or cooling, as desired by design. Appendage46 arrangements can be otherwise varied to affect and improve heatdissipation and thermal management of fuel cell stack 60 according toother specific designs. For example, appendages 46 need not span a sideof plate 44 as shown and may be tailored based on how the heating fluidis channeled through the housing.

A fuel cell system of the present invention may also include one or moresensors to help regulate thermal management. For example, a temperaturesensor may detect temperature for a component in the fuel processor 15,such as a sensor arranged within burner 30 for detecting temperatureswithin the burner. Other components in fuel processor 15 whosetemperature may be monitored by a sensor include: reformer 32, boiler34, boiler 108 and gases at the inlet at outlet ports of each of thesecomponents. A temperature sensor may also detect temperature for acomponent in fuel cell 20. For example, a sensor may be arranged incontact with the substrate 89 of one or more bi-polar plates 44 fordetecting the temperature of the plate. Other component in fuel cell 20whose temperature may be monitored by sensor include: MEA layer 62 andgases in an inlet or outlet manifold. Suitable temperature sensors foruse with the present invention are widely commercially available fromnumerous sources known to those of skill in the art.

Also described herein are catalyst containment systems for use with afuel cell. A catalyst containment system locates and holds a thermalcatalyst outside the fuel cell. As mentioned above, the thermal catalystcombines with the heating medium to catalytically generate heat fortransfer to a fuel cell. One or more walls of the catalyst containmentsystem may also facilitate heat transfer from the catalyst into the fuelcell.

FIGS. 5A-5C show three exemplary catalyst containment systems 500, 520and 540, respectively, that achieve catalyst containment in accordancewith three embodiments of the present invention.

Generally, the catalyst containment system includes a set of walls thatcontain the thermal catalyst outside the fuel cell. The set of wallspermit a heating medium to pass into the containment system and over thecatalyst. Each wall may be porous or non-porous. Suitable porous wallsinclude metal mesh materials and the like that allow a gas to passtherethough. Non-porous walls may include one or more walls that blockand guide gaseous flow in the containment system and over the catalyst.In this case, the heating medium enters the catalyst containment systemin one or more inlets and exits via one or more outlets (holes,apertures, etc.) in the walls. The non-porous walls may comprise a wallfor other components in the fuel cell system. For example, an outer wallof fuel cell 20, interconnect 190, an external housing, may form one ofthe walls in a catalyst containment system.

In one embodiment, the catalyst containment system uses a heat transferappendage 46 as one of the walls. As described above, a fuel cell mayinclude one or more heat transfer appendages (also referred to asthermal fins) that conduct heat into and out of a fuel cell stack. Inthis case, in addition to being a multifunctional heat sink, the heattransfer appendage also cooperates in the catalyst containment system tohold a thermal catalyst. Contact between the thermal catalyst and heattransfer appendage/wall permits conductive heat transfer from thecatalyst into the appendage, and then conductive heat transfer from theappendage into the fuel cell.

Referring first to FIG. 5A, a first catalyst containment system 500 hasa gap 502 between appendages 46 that receives and houses catalyst 504particles in between the appendages 46. Gap 502 may vary in size and canbe enlarged and vertically expanded at the cost of active surface areaof appendages 46 for the entire fuel cell stack. Gap 502 can also benarrowed by design and as permitted by catalyst 504 particle diameter.In one embodiment, gap 502 is from about 2 to about 5 millimeters. Inspecific embodiment, gap 502 is about 4 millimeters for catalyst 504particles with a diameter of about 3 millimeters. A non-porous outerwall 506 with one or more apertures for inlet and outlet then restsoutside the appendages 46 to contain catalyst 504 between the fuel cell20, appendages 46 and outer wall 506. Another set of walls (not shown)also contain catalyst 504 at either end of the channel betweenappendages 46. These walls may include inner walls of the housing orpackage that contains fuel cell 20. Alternatively, a wall of fuel cell20 may extend outward to cap the channels between appendages 46 ateither end (normal to the page).

The length of appendages 46 can be varied according to thermalrequirements, amount of catalyst 504, and fuel cell package spacepermit. In general, increasing appendage 46 length increases the size ofcatalyst containment system 500 and increases the ability of appendages46 to transfer heat (heat or cool).

Catalyst containment system 520 (FIG. 5B) includes a configuration thatincludes a smaller gap 522 and increases direct contact between catalyst504 and heat transfer appendages 46. The smaller gap 522 provides atighter packing volume for catalyst 504, which increases conductive heattransfer from the catalyst 504 to heat transfer appendages 46. Gap 522can be as narrow as permitted by the catalyst 504 particle diameter, andcan be thicker than the catalyst diameter to permit packing. In aspecific embodiment, gap 522 is from about 0.02 millimeters to about 5millimeters. In another specific embodiment, gap 522 is less than 2millimeters and the catalyst 504 particles have a diameter of about 1millimeter. A porous outer wall 526 rests outside the appendages 46 tocontain catalyst 504 between the fuel cell 20, appendages 46 and outerwall 526. Appendages 46 and gap 522 can be lengthened or shortened tooptimize the heating and cooling area, depending on space available in afuel cell.

Catalyst containment system 540 (FIG. 5C) includes an end wall 546 onthe distal end of each appendage 46 that extends normal to the appendage46 and above and below the appendage 46. Distal wall 546 helps containcatalyst 504, and cooperates with an outer wall of fuel cell 20 andappendages 46 to create a channel 548 between appendages 46 in which thecatalyst 504 is located. End wall 546 may include caps attached ontoeach appendage, or may be integrally formed with each appendage 46, forexample. Other ways to construct an end wall 546 in a fuel cell are alsosuitable for use herein. Containment system 540 provides a completewalling system and does not require any additional screens to containcatalyst 504. A clearance 549 between adjacent end walls 546 ensuresthat adjacent walls 546 do not touch and permits the heating medium toenter and exit. The size of clearance 549 is adjustable. In oneembodiment, clearance 549 is increased to improve flow of a heatingmedium to and from the thermal catalyst. As before, the gap betweenappendages 46 in system 540 and the extended length of each appendage 46can be modified based on required cooling and heating as well ascatalyst diameter.

In one embodiment, the present invention delivers a heating medium froma plumbing outlet that is in close proximity to a thermal catalyst,which heats a fuel cell. FIG. 6 shows a simplified illustration of thisproximal delivery in accordance with one embodiment of the presentinvention. As shown, a portion 561 of heat transfer appendage has beencut away to show a thermal catalyst 568 arranged in a catalyst bed 563(a contiguous volume of catalyst 568) between appendages 46 of fuel cell20.

In one embodiment, the exhaust is released within the walls of acontainment system or within the catalyst bed 563. In this case, aheating medium 566 (such as burner exhaust and fuel included therein) isforced to escape through catalyst bed 563 and thereby interact withadditional catalyst 568 as it escapes. This generates heat regardless ofescape velocity for heating medium 566. When the heating medium includesa high escape velocity, such as small molecule gases like hydrogen, thisimproves interaction between the heating medium and catalyst andgenerates more heat.

In general, proximity refers to the heating medium being released closeenough to the thermal catalyst 568 such that heat is generated at thecatalyst. In another embodiment, the heating medium is delivered andreleased outside the walls of a containment system and proximityincludes releasing the exhaust at a short distance to catalyst 568(which also incorporates releasing the heating medium within thecatalyst bed or containment system). Referring to FIG. 6, a distance 560from an outlet 562 of plumbing 564 to catalyst 568 in bed 563characterizes proximity between the two. It is understood that a thermalcatalyst 568 disposed in bed 563 covers a significant area. In thiscase, distance 560 refers to the shortest distance between the outlet562 of plumbing 564 and the nearest catalyst 568 in bed 563. In oneembodiment, distance 560 is less than about 2 centimeters. In anotherembodiment, distance 560 is less than about 1 centimeter. In a specificembodiment, distance 560 is less than about 5 millimeters. Distancesless than 2 millimeters are suitable in some cases. In a specificembodiment, the burner exhaust exits its delivery plumbing less thanabout 1 millimeter from the nearest catalyst 568. Other distances may beused as long as heat is generated in the catalyst.

Fan 37 moves the exhaust gases across the catalyst within the fuel cellhousing (not shown). In one embodiment, burner exhaust outlet 562 issituated closer to catalyst 568 than fan 37 such that burner exhaustgases do not substantially pre-mix with air. In other words, the burnerexhaust outlet 562 is positioned such that the burner exhaust gasestravel immediately from outlet 562 onto the catalyst 568 beforesignificantly mixing with any inlet air. As shown, the exhaust outlet562 is positioned closer to the thermal catalyst 568 than fan 37. Forsmall molecule gas heating mediums such as hydrogen, this reduces theeffect of the incoming air as a disturbance to the flow of the heatingmedium over the catalyst.

After passing across catalyst 568, the burner exhaust is then channeledout of fuel cell 20 in the direction of general airflow and fuel cellexhaust 567. Fuel cell 20 and its one or more exhaust ports 567 may bedesigned such that the burner exhaust 566 is drawn across additionalcatalyst before it exits the fuel cell. For example, outlet port 567 ispositioned such that a decreasing pressure gradient progresses from theburner exhaust outlet 562, across additional catalyst 568 in catalystbed 563 in the direction of outlet port 567, and then finally out thefuel cell 20. This increases the interaction between catalyst 568 andheating medium.

Dimensions and configuration of a catalyst containment system can bevaried to suit thermal requirements of the fuel cell system and catalystsize, as one of skill in the art will appreciate. In one embodiment, thethickness of the thermal fin system and integrated catalyst containmentsystem does not exceed the width of the bi-polar plate to ensure thatadjacent plates do not touch one another and thus avoid shorting out thestack.

Heating a fuel cell with a heating medium may also become undesirable attimes. The electrical generation process in fuel cell 20 is commonlyexothermic. When the fuel cell continuously generates electrical energy,methanol provision to the fuel cell's thermal catalyst adds to heatgenerated by the fuel cell and the fuel cell may become too hot. In oneembodiment to avoid overheating issues, the present invention places acontrol valve on a heating medium such as the burner exhaust thatcontrollably routes the heating medium to a) a thermal catalyst and/orfuel cell or b) away from the thermal catalyst and/or fuel cell, asdesired.

FIG. 6 shows such a cutoff valve 590 in accordance with one embodimentof the present invention. Valve 590 responds to control signals androutes the burner exhaust 566 away from the catalyst 568 when the fuelcell 20, or a portion thereof such as an MEA layer, surpasses athreshold temperature. In this case, valve 590 re-directs the burnerexhaust 568 to an exhaust line 592 for the fuel cell system that outletsthe burner exhaust 568 into the environment, via outlet port 594,outside a housing 595 for a package that includes the fuel cell 20 andfuel processor.

When burner exhaust is used as the heating medium, the same burner inletfuel stream may be used for two purposes: 1) heat generation in the fuelprocessor, and 2) heat generation for the fuel cell. In one embodiment,the fuel cell system includes controls that allow the amount of fuelprovided to the burner to be varied. Controlling the amount of methanol(or other fuel) provided to the burner permits the fuel cell system torun ‘rich’ or ‘lean’.

FIG. 7 shows a method 700 for providing fuel in a fuel cell system inaccordance with one embodiment of the present invention. In general,method 700 is suitable for use in any fuel cell system that includes afuel processor and fuel cell that share a burner fuel, and inparticular, is well suited for fuel cell systems where thermalefficiency is important.

Method 700 begins by running the fuel ‘lean’ and providing fuel to aburner in the fuel processor (702). Lean fuel provision provides enoughmethanol to heat a reformer or fuel processor. Lean methanol provisionto a burner feed implies that the amount of methanol currently beingsupplied is sufficient to maintain a desired degree of heat generationin one or more portions of a fuel processor, or to maintain a desiredoperating temperature in the reformer. For example, the required amountof methanol provision and heat generation may be determined by theamount of hydrogen currently being generated or a minimum reformingtemperature needed by the reforming catalyst. Suitable burners, pumps,valves, plumbing, fuels, and fuel storage cartridges were describedabove.

The fuel is then catalytically combusted in the burner to generate heat(704). At least a portion of the heat from the burner transfers to areformer included in the fuel processor (706). Monolithic structuresdescribed above transfer the heat via conduction through walls shared bythe burner and reformer. Some of the heat may also transfer to a boilerin the fuel processor that vaporizes fuel for the burner, and to aboiler that vaporizes fuel for the reformer. An electrical heater mayalso be used to vaporize the incoming burner fuel, e.g., during startupbefore the burner and burner's boiler are hot enough to vaporize theincoming fuel.

A decision is then made to run the inlet burner fuel rich or lean (706).Rich methanol provision provides more methanol to the burner than anamount of methanol that can be consumed according to the amount ofcatalyst contained in the burner. As a result, the burner exhaustincludes unused methanol. When the burner exhaust is provided to acatalyst configured to heat a fuel cell, the rich methanol provisionoffers methanol in the exhaust that both catalytically heats the fuelcell and fuel processor.

If a decision is made at 706 to heat the fuel cell using the burnerexhaust, method 700 increases the amount of fuel provided to theburner—such that more fuel is provided to the burner than is combustedin the burner to generate heat for the fuel processor (708). Plumbingthen transports the burner exhaust from the burner to a thermal catalystthat produces heat when the burner exhaust passes over the thermalcatalyst (710).

The heat transfers from the thermal catalyst to the fuel cell (712).Suitable catalyst containment systems were described above, but method700 is not limited by these configurations and may employ other designsfor transferring heat from a catalyst into the fuel cell, such ascatalyst beds that are internal to the fuel cell and between layers. Aheat transfer pipe may also be used to conduct heat from a catalyst thatis remote from the fuel cell (see FIG. 8).

The rich methanol provision continues until a threshold temperature forthe fuel cell has been reached (714 back to 710). The thresholdtemperature may correspond to an initial operating temperature of thefuel cell, for example. Once the threshold temperature has been reached,the fuel supply returns to lean provision (702). A pump, or othercontrolled source of fuel delivery, transports the fuel to the burnerand carries out the lean/rich provision. Since the amount of fuelconsumed in the burner is known, supplying added fuel using the pumpthen enables a rich feed. In conjunction with suitable control, such asdigital control applied by a processor that implements instructions fromstored software, the burner fuel pump responds to control signals fromthe processor and moves a desired amount of rich or lean methanol fromthe storage device to the burner. It is important to note that thecontrol in this regard is not necessarily binary (e.g., rich or lean)and may include varying degrees of rich and lean methanol provision. Forexample, temperature levels, thermal efficiency, and/or fuel efficiencymay all affect rich/lean fuel provision levels. A sensor may also beused to read the fuel cell temperature and output feedback to theprocessor.

Running the methanol provisional rich through the burner eliminates theneed for a separate fan or pump that solely services fuel provision to athermal catalyst in the fuel cell. This simplifies fuel cell systemcomplexity, and reduces overall size of a portable fuel cell system. Italso efficiently uses heat that vaporizes the burner fuel to doubly doso for both the fuel processor and fuel cell. Running the methanolacross the fuel cell catalyst also functions as an exhaust clean-up byconsuming any unused methanol in the (rich or lean) fuel processorexhaust before it exits the fuel cell system into the ambientenvironment.

A fuel cell system of the present invention may employ other burnerexhaust configurations. FIG. 8 shows a fuel cell system 800 inaccordance with another embodiment of the present invention. System 800includes fuel processor 15, fuel cell 20, fluid lines 802-810, thermalcatalyst 812, valve 815, emissions catalyst 814, heat pipe 816, heatpipe 818, heat sink 820 and housing 822.

Valve 815 receives burner exhaust 805 from the burner in fuel processor15 via line 802 and directs flow of the burner exhaust 805 between line804 and line 806.

Line 804 communicates the exhaust 805 to emissions catalyst 814, whichremoves the fuel and unwanted chemicals from exhaust 805 beforereleasing the exhaust 805 into the environment 811 external to the fuelcell system package or housing 822. Unwanted chemicals removed fromexhaust 805 include the fuel (e.g., methanol), products of thecombustion in the burner 30, carbon monoxide, formaldehyde, methanol andhydrogen for example. Other exhaust components may also be filtered out,as one of skill in the art will appreciate. Emissions catalyst 814 maycomprise any suitable catalyst for removing the unwanted chemicals fromexhaust 805.

In one embodiment, catalyst 814 and the methanol in exhaust 805 react togenerate heat. In this case, a fan 817 convects the heat away from fuelcell 20 and out of the package 822. A converging/diverging nozzle 825includes a low negative pressure change that promotes fan flow andexhaust dilution into environment 811. Emissions catalyst 814 is alsosuitably distant from fuel cell 20 such that the catalytically generatedheat does not convect or otherwise transfer to fuel cell 20. Suitableemissions catalyst 814 include platinum or palladium or any of thoselisted above with respect to burner 30 of FIG. 2A. Other catalysts maybe used.

Line 806 communicates exhaust 805 to remote thermal catalyst 812, whichgenerates heat to warm fuel cell 20. In this case, however, heattransfer pipe (or ‘heat pipe’) 816 separates remote catalyst 812 fromfuel cell 20 and conductively transfers heat from catalyst 812 to fuelcell 20. This embodiment transfers heat less efficiently than the systemshown in FIG. 5, but also separates fuel cell 20 from theheat-generating thermal catalyst 812 and thermally isolates the twocomponents so that heat from catalyst 812 can be controllably providedto the fuel cell (to avoid overheating the fuel cell). This alsosimplifies plumbing around fuel cell 20. In a specific embodiment, heatpipe 816 is configured to conductively transfer heat from thermalcatalyst 812 to an internal portion of the fuel cell stack. In thiscase, metal from the heat pipe 816 is brazed of otherwise in conductivethermal communication with internal portions of the fuel cell stack. Oneor more heat transfer appendages 46 may be used in this regard. In aspecific embodiment, catalyst 812 is at least about one centimeter fromfuel cell 20. Other distances may be used to thermally isolate the twocomponents.

Valve 815 thus directs burner exhaust 805 to remote catalyst 812 whenfuel cell 20 needs heat (e.g., during startup or long periods ofinactivity), and diverts the exhaust 805 to emissions catalyst 814 whenfuel cell 20 does not need heat.

A second heat pipe 818 conductively removes heat from fuel cell 20. Whenfuel cell 20 needs cooling, a fan blows air across heat sink 820, whichopens to the environment 811 outside package 822. This draws and sinksheat from fuel cell 20. Fan 821 is then controlled as desired, to drawheat and cool fuel cell 20. In another embodiment, fan 821 is notincluded and heat pipe 818 conducts directly to a vent or radial finswithout any active control or heat sink.

Heat pipes 821 and 816 in system 800 include one or more thermalconductors, such as one or more copper (or another metal) structuresconfigured to conductively transfer heat. One of skill in the art isaware of the various techniques to conductively transfer heat betweentwo locations, and the present invention is limited by any specificdesign to conductively transfer heat.

Together, heating with valve 815 and remote thermal catalyst 812 combinewith cooling with fan 821 and heat sink 820 to permit heating andcooling control for fuel cell 20. Suitable control, such as digitalcontrol applied by a processor that implements instructions from storedsoftware, then controls valve 815 and fan 821 to regulate fuel cell 20within a desired temperature range. A temperature sensor may also beincluded in system 800 to read temperature of fuel cell 20 and outputfeedback to the processor.

System 800 may also run rich/lean according to method 700 of FIG. 7.When fuel cell 20 needs heat and exhaust 805 runs rich (708), valve 815diverts the exhaust 805 into remote thermal catalyst 812 (710), and theheat generated using catalyst 812 conducts via heat pipe 816 to fuelcell 20 (712). At this time, fan 821 is off. The exhaust from catalyst812 continues to emissions catalyst 814 for cleansing any remaining fuelin the exhaust before releasing into environment 811.

Exhaust 805 runs lean (702-706) when fuel cell 20 is exothermicallygenerating heat and does not need heat. Valve 815 then diverts exhaust805 to emissions catalyst 814 before releasing the exhaust 805 intoenvironment 811. Valve 815 thus avoids overheating fuel cell 20 when toomuch unburned fuel is in exhaust 805. Also if the fuel cell is above athreshold high temperature, fan 821 turns on and actively cools fuelcell 20.

The present invention also increases thermal and overall efficiency of aportable fuel cell system by using waste heat in the system to heatincoming fuel. FIG. 9 shows a fuel cell system 900 that includes arecuperator 902 in accordance with one embodiment of the presentinvention.

Recuperator 902 transfers heat from fuel cell system 900 to the inletfuel 17 before the methanol reaches fuel processor 15. While system 900shows recuperator 902 heating methanol in line 29 that carries fuel 17to the boiler 34 and reformer 32, it is understood that recuperator 902may be used to heat methanol in line 27 that carries fuel 17 to theburner 30.

Broadly speaking, recuperator 902 may include any device fortransferring heat produced in fuel cell system 900 or a heated gasproduced in fuel cell system 900 to the incoming fuel 17. Recuperator902 may include one or more heat transfer channels for moving theincoming fuel 17, moving the heating medium, and one or more surfaces orstructures for transferring heat from the heating medium to the incomingfuel 17. In one embodiment, recuperator 902 includes a commerciallyavailable heat exchanger. Recuperator 902 may rely on conductive heattransfer, convective heat transfer, and combinations thereof.

In one embodiment, the heat used to warm fuel 17 comes from a fluid infuel cell system 900. Fluids (a gas or liquid) suitable for use in thismanner include: the cathode exhaust from fuel cell 20 in line 33, thereformer 32 exhaust from fuel processor 15 (see FIG. 4), the burner 34exhaust from fuel processor 15 in line 35, the anode exhaust from fuelcell 20 in line 38, or combinations thereof. Fuel cell 20 and fuelprocessor 15 both run at elevated temperatures during steady-stateoperation. Any fluids emitted from fuel cell 20 and fuel processor 15will also be at elevated temperatures and are suitable for heat transferto the incoming fuel.

As mentioned before, incoming fuel to a reformer 32 in fuel processor 15is vaporized before processing by a reforming catalyst in the fuelprocessor. Similarly, incoming methanol to burner 30 is vaporized beforemeeting the burner catalyst. The fuel 17 typically enters the fuel cellpackage at its storage temperature in storage device 16, which isnormally cooler than the operating temperatures of fuel cell 20 and fuelprocessor 15, or fluids emitted from these devices. Any heat transferredto fuel 17 before vaporization in fuel processor 15 reduces the amountof energy that the heater in fuel processor 15 supplies to the fuel 17.This increases efficiency by i) leaving more heat for the reformer andcatalytic production of hydrogen and/or ii) consuming less fuel to heatfuel processor 15. This also reduces the burner exhaust temperatureleaving the package. For an electrical heater that vaporizes theincoming methanol, this reduces electrical energy used by the electricalheater to vaporize the incoming fuel.

A wide variety of heat exchanging devices are suitable for use herein totransfer heat from the heating medium in system 900 to the incomingfuel. FIGS. 10A-10C show three exemplary recuperators 902 a-902 c,respectively, in accordance with the present invention.

Recuperator 902 a attaches to a wall 904 disposed between fuel cell 20and fuel processor 15 that faces fuel cell 20. Line 29 carries the fuelfrom storage device 16 (FIG. 1B) and enters recuperator 902 a at hole912. The fuel then travels through recuperator 902 a to a high-surfacearea portion 906 of line 29 in recuperator 902 a. Portion 906 wrapsaround line 35 and provides a large surface area for thermal interactionwith the walls of line 35. As shown in FIG. 1B or 9, line 35 transportsthe burner exhaust from fuel processor 15 to fuel cell 20. Heat in theburner exhaust thus: a) convects from the burner exhaust to the walls ofline 35, conducts through the walls of recuperator 902 a to the walls ofhigh-surface area portion 906, and c) convects from the walls ofhigh-surface area portion 906 into the fuel in line 29. The heated fuelthen continues through line 29 to hole 910 for further transport to aninlet of the fuel processor.

If the operating temperature of recuperator 902 a is less than anadjacent fuel cell or fuel processor, then the recuperator may sinksheat from the warmer structures and reduce efficiency. FIG. 10B shows arecuperator 902 b that is physically separated from the fuel processor15, which reduces heat transfer and loss from the fuel processor 15 tothe recuperator 902 b. Situating recuperator 902 b in a space that isnot between fuel cell 20 and fuel processor 15 also permits a largerrecuperator 902 b.

The larger recuperator 902 b also permits longer flow paths for theburner exhaust and inlet fuel, which provides more time for heattransfer. Burner exhaust, shown by dotted line 920 in FIG. 10B, startsat an exit of the burner in fuel processor 15 and linearly runs thelength of recuperator 902, twice, before routing back to port 922, whichopens to the thermal catalyst used to heat the fuel cell. The inlet fuelpath, shown by dotted line 924, starts at a fuel inlet and linearly runsthe length of recuperator 902, twice, before provision into the burnerinlet (internal and not shown) of fuel processor 15. In this case, gasin burner exhaust 920 runs counterflow to fuel in fuel path 924.

Recuperator 902 c (FIG. 10C) is similar recuperator 902 b except itnon-linear plumbing, in the recuperator, that transports the reformerfuel or the burner fuel. As shown, the plumbing in recuperator 902 cfollows a curved flow path for both burner exhaust 920 and fuel path924, which permits longer flow paths for the burner exhaust and inletfuel and further improves heat transfer from the exhaust to the fuel.

Thermal efficiency of the present invention may also manage heat lossfrom a fuel cell system package. Many fuel cells and fuel processorsoperate at elevated temperatures. Burner 30 temperatures from about 200degrees Celsius to about 800 degrees Celsius are common. Many fuel cells20 operate at elevated temperatures during electrical energy production.The electrochemical reaction responsible for hydrogen consumption andelectrical energy generation typically requires an elevated temperature.Start temperatures in the MEA layer 62 and its constituent parts greaterthan 150 degrees Celsius are common.

The ambient environment around the fuel cell package is cooler, andtypically less than 40 degrees Celsius. Heat loss from a fuel cell orfuel processor to the ambient environment decreases efficiency of eachdevice, and of the fuel cell system.

In one embodiment, a fuel cell package of the present invention includesan insulation arrangement that reduces heat loss from a fuel cell or afuel processor. The insulation arrangement includes one or more layersof insulation that are disposed at least partially between a fuel celland/or fuel processor and a package housing. The insulation arrangementreduces heat transfer from the fuel cell and/or fuel processor to thepackage housing, which reduces temperatures for the housing. This inturn reduces heat loss to the ambient environment. Thus, the insulationarrangement keeps heat in the portable package and increases efficiencyfor the system components running at elevated temperatures.

FIG. 11 shows a simplified cross section of a fuel cell system thatincludes an insulation arrangement 1000 in accordance with a specificembodiment of the present invention. The fuel cell system includes aheat-generating component 1001, such as a fuel cell or fuel processorthat generates heat.

Above the heat-generating component 1001, arrangement 1000 includes (inorder of outward layering in cross section): a first layer of insulation1008 a, a second layer of insulation 1008 b, a non-conductive membranelayer 1004 a, spacing structure 1006, a second non-conductive membranelayer 1004 b, and top package wall 1002.

Below the heat-generating component 1001, arrangement 1000 includes: afirst layer of bottom insulation 1008 c, a second layer of insulation1008 d, a non-conductive membrane layer 1004 c, and bottom package wall1012.

Insulation layers 1008 a-d is disposed at least partially around theoutside of component 1001 to minimize heat loss therefrom. Insulation1008 may include one or more layers of a low thermal conductancematerial. In a specific embodiment, insulation 1008 wraps around thefuel cell 20, fuel processor 15 and/or fuel cell system package.Thickness for the insulation 1008 layer and the number of wrappingsaround each heat-generating component 1001 may be varied according todesign. Increasing the thickness or the number of wrappings decreasesheat loss but increases package thickness and is varied according todesign. A thickness for insulation 1008 from about 1 millimeter to about10 millimeters is suitable for some designs. In another specificembodiment, insulation 1008 has a thickness of about 2 millimeters andis wrapped twice about the fuel cell and fuel processor. Insulation 1008may include a commercially available sheet of insulation. One suitablecommercially available insulation material comprises aerogel insulationas provided by Aspen Systems, Inc. of Marlborough, Mass. Other forms ofinsulation may be used. One of skill in the art will appreciate the widevariety of commercially available insulation products useful herein toachieve a desired temperature drop.

Spacing structure 1006 includes a porous cross section with air gaps1007. The gaps 1007 may be configured as channels (e.g., normal to thepage) that permit airflow 4therethrough. In one embodiment, a fan movesair through the gaps 1007 to facilitate heat dissipation away fromsurface 1015.

Each non-conductive membrane layer 1004 a-c includes a thin rigid sheetwith low thermal conductivity. The low thermal conductivity of membranelayer 1004 reduces heat transfer out of the package. The rigidity ofmembrane layer 1004 prevents the compliant insulation layer 1008 b fromextruding into spacing structure 1006 and reducing the size of air gaps1007. In a specific embodiment, each non-conductive membrane layer 1004includes a thin layer of mica paper, e.g., about 0.5 millimeters thick.Other materials and thicknesses are suitable for use.

Top package wall 1002 and bottom package wall 1012 represent the outsidewalls of a portable package the contains the fuel cell system. As shown,the inner surfaces of top and bottom walls 1002 and 1012 include aporous, ribbed, baffled or pinned structure that also creates airchannels 1111. Similar to gaps 1007, channels 1111 may be configured aschannels that permit airflow therethrough. In one embodiment, a fanmoves air through the gaps 1111 to facilitate heat dissipation away fromsurface 1015. This can be the same fan that moves air through gaps 1007.

Arrangement 1000 thus includes a number of insulation layers and layertypes that can be varied according to design. For example, the crosssection above and below the heat-generating component 1001 provides twoexamples of insulation arrangement 1000 between component 1001 and outersurface 1015. In another embodiment, gaps 1007 may be disposed solelybetween insulation 1008 and package wall, between insulation 1008 andcomponent 1001, etc. In one embodiment, layers and layer types ininsulation arrangement 1000 are selected and configured such that theoutside surface 1015 of a fuel cell package maintains a desiredtemperature. Standards imposed on consumer-electronics devices maymandate surface temperature of electronics devices such as a tetheredfuel cell package to be less than some predetermined level, andinsulation arrangement 1000 may be designed to regularly meet thislevel. Some consumer-electronics device standards require a surfacetemperature less than 50° C. In another specific embodiment, aninsulation layer 1008 is disposed around component 1001 in addition to alayer of insulation 1008 around the fuel cell system package 1015. Thisdual insulation set further maintains heat in the heat generatingcomponents of the fuel cell system.

While this invention has been described in terms of several preferredembodiments, there are alterations, permutations, and equivalents thatfall within the scope of this invention which have been omitted forbrevity's sake. For example, although the present invention hasdescribed fuel processors in a portable fuel cell systems, it is notrelated to small or portable systems. In addition, heating systems havebeen described with respect to fuel cells that include heat transferappendages. It is understood that the present invention need not includeone or more heat transfer appendages. It is therefore intended that thescope of the invention should be determined with reference to theappended claims.

1. A portable fuel cell system for producing electrical energy, theportable fuel cell system comprising: a fuel processor that includes areformer configured to receive reformer fuel and including a catalystthat facilitates the production of hydrogen from the reformer fuel, anda burner configured to i) catalytically process burner fuel to generateheat and ii) output burner exhaust; a fuel cell including a fuel cellstack configured to produce electrical energy using hydrogen output bythe fuel processor, a set of bi-polar plates included in the fuel cellstack, wherein each bi-polar plate includes a thickness that is lessthan about 2 millimeters, and a set of heat transfer appendages, whereineach heat transfer appendage includes a portion arranged external to thefuel cell stack and is in conductive thermal communication with abi-polar plate in the set of bi-polar plates; a thermal catalyst,disposed outside the fuel cell and in conductive thermal communicationwith the set of heat transfer appendages, operable to produce heat whenthe burner exhaust interacts with the thermal catalyst; and plumbingconfigured to controllably transport the burner exhaust to the thermalcatalyst, wherein the plumbing includes a valve that directs the burnerexhaust a) to the thermal catalyst or b) to a line that transports theburner exhaust away from the thermal catalyst, and wherein an outlet ofthe plumbing is less than about 2 centimeters from the thermal catalystnearest to the outlet.
 2. The fuel cell system of claim 1 wherein thethermal catalyst is included in a catalyst containment system thatincludes a set of walls configured to hold the thermal catalyst outsidethe fuel cell and permit the heating medium to pass into the catalystcontainment system.
 3. The fuel cell system of claim 2 wherein the heattransfer appendage forms one of the set of walls.
 4. The fuel cellsystem of claim 2 further comprising an end wall on the distal end theheat transfer appendage that extends normal to the appendage and aboveand below the appendage.
 5. The fuel cell system of claim 1 wherein theline that transports the burner exhaust is configured to transport theburner exhaust to an emissions catalyst that is configured to remove thefuel from the burner exhaust before the burner exhaust exits a housingfor the fuel cell system.
 6. The fuel cell system of claim 5 wherein theburner exhaust includes methanol.
 7. The fuel cell system of claim 1further comprising a heat transfer pipe configured to conductivelytransfer heat from the thermal catalyst to the fuel cell stack.
 8. Thefuel cell system of claim 7 wherein the heat transfer pipe is configuredto conductively transfer heat from the thermal catalyst to an internalportion of the fuel cell stack.
 9. The fuel cell system of claim 1further comprising: a heat sink in conductive thermal communication withthe fuel cell using a heat transfer pipe configured to conductivelytransfer heat from the fuel cell to the heat sink; and a cooling fanconfigured to cool the heat sink.
 10. A portable fuel cell system forproducing electrical energy, the portable fuel cell system comprising: afuel processor that includes a reformer configured to receive reformerfuel and including a catalyst that facilitates the production ofhydrogen from the reformer fuel, and a burner configured tocatalytically process burner fuel to generate heat; a fuel cellincluding a fuel cell stack configured to produce electrical energyusing hydrogen output by the fuel processor, a set of bi-polar platesincluded in the fuel cell stack, wherein each bi-polar plate includes athickness that is less than about 2 millimeters, and a set of heattransfer appendages, wherein each heat transfer appendage includes aportion arranged external to the fuel cell stack and is in conductivethermal communication with a bi-polar plate in the set of bi-polarplates; a catalyst containment system that includes a set of wallsconfigured to hold a thermal catalyst outside the fuel cell and permit aheating medium to pass into the catalyst containment system, wherein thethermal catalyst and heating medium are selected to produce heat whenthe heating medium interacts with the thermal catalyst; and plumbingconfigured to transport the heating medium to the catalyst containmentsystem, wherein an outlet of the plumbing is less than about 2centimeters from thermal catalyst nearest to the outlet.
 11. The fuelcell system of claim 10 wherein the plumbing is configured to releasethe heating medium within the walls of the containment system.
 12. Thefuel cell system of claim 10 wherein an outlet of the plumbing is lessthan about 1 centimeter from the thermal catalyst nearest to the outlet.13. The fuel cell system of claim 12 wherein an outlet of the plumbingis less than about 2 millimeters from the thermal catalyst nearest tothe outlet.
 14. The fuel cell system of claim 10 wherein the heatingmedium includes exhaust from the burner and the plumbing is configuredto transport the burner exhaust from the burner to the catalystcontainment system.
 15. The fuel cell system of claim 14 wherein theburner exhaust includes unused methanol.
 16. The fuel cell system ofclaim 10 further comprising a heat transfer pipe configured toconductively transfer heat from the catalyst containment system to thefuel cell stack.
 17. The fuel cell system of claim 16 wherein the heattransfer pipe is configured to conductively transfer heat from thethermal catalyst to an internal portion of the fuel cell stack.
 18. Thefuel cell system of claim 10 wherein the heat transfer appendage formsone of the set of walls of the catalyst containment system.
 19. The fuelcell system of claim 18 wherein the plumbing includes a valve thatdirects the burner exhaust a) to the thermal catalyst or b) to a linethat transports the burner exhaust away from the thermal catalyst. 20.The fuel cell system of claim 19 wherein the line transports the burnerexhaust outside a housing wall for a portable package that contains thefuel cell system.